Cartridge fuse



.NOV. 4, 1947. A BERTHEL 2,430,041

CARTRIDGE FUSE Filed 001, 7, 1945 2 Sheets-Sheet 1 G. A. BERTHEL CARTRIDGE FUSE Nov. 4, 1947.

Filed Oct. 7, 1943 2 Sheets-Sheet 2 um w a t m Patented Nov. 4, 1947 CARTRIDGE FUSE Gust A. Berthel, Chicago, Ill., assignor to Jefferson Electric Company, Bellwood, 111., a corporation of Illinois Application October 7, 1943, Serial No. 505,261

13 Claims. 1

This invention relates to improvements in cartridge fuses, and in particular to those of the knife blade type.

This type of fuse has commonly consisted of a casing, a terminal blade unit disposed Within the casing, the blades of which project from either end, and end caps fitting over the terminal blades and secured to the casing. The casing consists of a short length tubing of vulcanized fiber fitted with brass ferrules at either end. The end caps are commonly of brass and are screw-threaded onto the ferrules. The replaceable fusible element is carried on the terminal blade unit and disposed within the fiber tube.

The brass ferrules and caps are screw machine products, and consequently, they are of substantial thickness. According to the present invention, the waste of such thickness may be avoided. Furthermore, it is entirely feasible to use steel in place of brass for the ferrules and caps. This is for the reason that the heating effect is reduced to a minimum due to the smaller cross section of the magnetic material in which eddy currents can be induced. It is impractical to make the ferrules and caps of steel on a screw machine, for the reason that it is a much slower operation. Furthermore, the thickness of these parts if made of steel cause eddy currents to be generated which have the effect of heatin up not onl the steel parts but also the adjacent parts to an undesirable extent, thereby changing the characteristics of the fuse.

It is an object of my invention to provide an improved fuse construction in which stamped or drawn sheet metal parts may be substituted for screw machine products in the non-current-carrying metal parts.

Another object is to provide an improved cartridge fuse construction which can be disassembled and assembled quickly for purposes of reloading.

A further object is to provide a fuse havin an improved venting means so that the gas created by the blowing of the fuse is permitted to escape at the proper rate, sufficiently fast to avoid rupture of the fiber tube, but still slow enough to build up sufficient pressure within the casing to smother the arc. This gas is bafiled in the form of a sheet flow along exterior metal parts so that it may be cooled well below the ignition point of such combustible materials as might have accumulated adjacent the fuse.

Another object is to provide an improved construction whereby the caps are secured directly to the terminal blade unit, which latter embodies an adjustable bridge; the caps also being associated with the casing in such a manner as to prevent separation of the caps and the terminal blades from the casing when the fuse blows.

Still another object is to provide in combination with a venting arrangement wherein the gas generated on blowing is bafiled along the skirt of the cap, an improved means of associating the cap with the terminal blade unit in gas-tight relationship to insure proper baffling,

Other objects, features and advantages will appear as this description proceeds.

With reference now to the drawings, in which like reference numerals represent like parts- Fig. 1 is an elevation of a preferred embodiment of my invention in its completely assembled form;

Fig. 2 is a section of the fuse shown in the position of Fig. 1;

Fig. 3 is a section taken along line 3-3 of Fig. 2;

Fig. 4 is an end view of the fuse, a portion of the cap being broken away;

Fig. 5 is a section taken along the line 5-5 of Fig. 6 is an end view of the casing, showing the ferrule construction;

Fig. 7 is an elevation of one of the slotted end washers; and

Fig, 8 is a detailed bottom plan view, showing the manner in which an end of the adjustable bridge is mounted.

As shown in Figs. 1 and 2, the fuse comprises a casing designated generally by the reference numeral I0, end caps II and I2, and a terminal blade unit designated generally by the reference numeral l3.

The casing comprises a short length of tubing I4 of vulcanized fiber, which is provided with ferrules l5 and I6 at its ends. The inner edges of these ferrules are crimped, as shown at IT and I8, so that they bite into the tubing l4, in order that the ferrules may be securely held in place against the considerable gas pressure Which is generated when the fuse is blown. A series of rivets may also be employed to securely fasten the ferrule l5 to the tubing 14, and a similar series of rivets 66 may be employed for the ferrule Hi. The ferrules l5 and I6 are also provided with segmental threads l9 and 20, respectively.

The terminal blade unit l3 comprises a terminal blade 2| disposed at the left hand end 01' the fuse, as shown in Figs. 1, 2 and 3, and a terminal blade 22 disposed at the right hand end of the fuse.

At the inner end of the terminal blades are disposed short lengths of U-shaped channels 23 and 24, respectively, which are secured to the terminal blades by screws 25 and 26, respectively. The channels 23 and 24 are each provided with oppositely disposed pending portions 21 and 28, respectively, which embrace a bridge member 35. Lugs 29 and 35 project from the depending portions 27 and 28 and are bent up underneath the bridge 35 and serve to hold it in position.

The lower edges of the side portions of the channels, at points adjacent to the depending portions 21 and 23, abut the upper surface of the bridge 35 and form shoulders 3| and 32 for each of the channel members '23 and 24, respectively. The bridge 35 is cut away along its side edges, as indicated at 33 and 34, in order to receive the depending portions 21 and 28. The bent over lugs 29 and 35 securely grip the bridge 35 against the shoulders 3| and 32 so that the bridge is substantially rigidly secured to the terminal blades 2| and 22.

It will be observed that the notched or cut away portions 33 and 34 are of greater width than the depending portions 21 and 28. This permits the position of the bridge to be adjusted with respect to either one of the terminal blades 2| or 22, this adjustment being in the nature of a sliding adjustment by means of which the overall length of the terminal blade unit |3 can be regulated. The bridge 35 is also made of vulcanized fiber. The vulcanized fiber has the property of absorbing moisture from the atmosphere which may change its length. Also temperature variations may change its length. The change of length of the fiber tubing |4 may not be the same as the change in length of the bridge 35; hence it has been found advisable to provide adjustable means for mounting the bridge 35 on the terminal blades 2| and 22. An analogous form of adjustable bridge construction is more fully disclosed and claimed in United States Letters Patent No. 1,854,450, granted April 19, 1932, on an application filed by H. R. Cook.

A fusible link 35 is mounted on the terminal blade unit by means of bolts 3! and 38 which pass through suitable apertures in the terminal blades 2| and 22 and are threaded into the U- shaped channels 23 and 24, as shown in Fig. 2. The fusible link 36 is provided with notches 4| and 42 at its ends, in order to facilitate replacement. One of these notches, 4|, may be longitudinally disposed, and the other notch, 42, may be transversely disposed, as shown in Fig. 3. The fusible link is gripped at its ends between washers 39 and 43 and the terminal blades 2| and 22, in order to make good electrical contact.

In operation, it will be seen that the terminal blade 2|, fusible link 35, and terminal blade 22 are in circuit with each other. Also the terminal blade unit as a whole is adjustably held together by the bridge 35 which forms a unit which is substantially rigid in the sense that it is resistant to torque and to bending.

The caps l and |2 are secured to the terminal blade unit I3 and cooperate with the casing ID to completely enclose the central portion of the terminal blade unit, including the fusible link 35 and the bridge 35. The arrangement is such that the gas which is generated upon the blowing of the fuse is deflected backwardly between the skirts of the caps H and l2 and the ferrules and H5 about which the caps are disposed.

Yoke washers 43 and 44 are positioned on the terminal blades 2| and 22, respectively, by means of staking, as indicated at 45 and 46. As seen in Fig. 3, that portion of the terminal blade 2| which is disposed to the right of the yoke washer 43 is of less width than that portion of the terminal blade which is disposed eXteriorly of the casing. This forms a shoulder against which the yoke washer 43 abuts, and this construction, together with the staking, not only forms a rigid assembly but also prevents the escape of gas along the joint between the yoke washer 43 and the terminal blade 2|. This same construction is present at the right hand end of the fuse as viewed in Figs. 2 and 3.

The ferrules l5 and I6 are provided with inturned flanges 41 and 48 which cover the ends of the tubing |4. These flanges 41 and 48 are provided with nibs 49 which serve to space slotted end washers 5| and 52 from the flanges 41 and 48 to permit the escape of gas in a radial direction. The slotted end washers 5| and 52 are fitted over the terminal blades 2| and 22 and are tightly fitted into engagement with the yoke washers 43 and 44 by means hereinafter described.

The terminal blades 2| and 22 are formed with oppositely disposed slots 53 and 54, respectively, which extend from each edge of each blade inwardly for an appreciable distance. The caps H and I2 are provided with Openings 55 and 56, as shown in Fig. 4, so that the caps may be fitted over the terminal blades and then twisted into interlocking engagement. The caps are also formed with pairs of wedge shaped embossings 51 and 58 on their end surfaces, which, when the caps are twisted, engage shoulders 13 and 14 which are formed by the slots 53 and 54. This construction serves to urge the slotted end washers 5| and 52 tightly against the yoke washers 43 and 44 so as to minimize the possibility of the escape of gas in a centripetal direction between their contacting surfaces, and then outwardly along the joint between the blades 2| and 22 and the slots in the slotted end washers 5| and 52, respectively. It will thus be seen that the caps H and |2 are securely associated with the terminal blade assembly in gastight relationship.

The caps II and I2 are also provided on their skirts with segmental threads 59 and 60, respectively, which are adapted to cooperate with the segmental threads I9 and 20 which are formed on the ferrules I5 and [6. These threads do not need to be in operative engagement with each other in the normal use of the fuse, for the reason that the caps are held in assembled position by their interlockin engagement with the terminal blades. However, these segmental threads do prevent outward movement of the caps when the fuse is blown. Without the engagement provided by these cooperating segmental threads, the adjustable bridge construction would permit the caps to fly outwardly with explosive violence when the fuse is blown. The segmental threads I 9 and 20 may preferably be about degrees in extent to permit easy insertion of the caps II and I2, whose segmental threads are about degrees in extent.

The casing H! is held in the proper angular position with respect to the terminal blade unit, so that a single quarter turn of either of the caps will bring the segmental threads into cooperating position, by means which interlock with the slotted end Washers 5| and 52. As shown in Fig 7, the slotted end washer 52 is provided with oppositely disposed marginal slots 82, and the end washer 51 is provided with similar marginal slots 6|. These pairs of marginal slots are engaged by pairs of lugs 63 and 64 which are struck up from the flanges 41 and 48 on the ferrules l5 and I6 in order to provide the interlocking relationship above mentioned.

I have found it advisable to upset the end of one of the terminal blades, such as the terminal blade 2 I, as shown in Figs. 1, 2 and 3 by the reference numeral 61, in such a manner as to prevent the complete removal of the cap I l I have also found it advisable to spot weld together the yoke washer 43 and the slotted end washer 5|, inasmuch as it is necessary to have complete separability of these elements at only one end of the fuse.

It will be noted that there is a clearance 69 between the yoke washer t4 and the wall of the casing it, to permit the escape of gas. There is also a clearance 10 between the end of the casing l and the slotted end washer 52, this clearance being insured by the presence of the nibs 50 on the ferrule 55. There is also a clearance H between the cap l2 and the ferrule Hi. All of these clearances, 65, i0 and N, form chambers which are in communication with each other, and form a bafiling means by which the hot gases generated by the blowing of the fuse may be vented to the atmosphere. As the gas flows along the inner surface of the skirt of cap l2, there will be a certain amount of heat exchange between the gas and this externally exposed part, which will serve to lower the temperature of the gas to a safe point.

In operation, the fusible link 36, preferably of the notched type as shown in the drawings, is secured to the terminal blade assembly by means of the bolts 31 and 38, At this stage, the cap ll ils loosely disposed on the terminal blade 2|, and the cap I2 and the slotted end washer 52 are entirely removed from the terminal blade 22, as is the casing H3.

The casing I0 is then slipped over the terminal blade unit so that the lugs 63 engage the marginal slots 6! formed in the slotted end washer Thus the casing is maintained in the proper angular relationship to the terminal blade unit so that when the cap is brought up into engagement with the slotted end washer 5|, the segmental threads 59 on the cap II will clear the segmental threads E9 on the ferrule [5. The cap is then given about a quarter turn which looks it into position with the terminal blade 2| and the casing 10.

The slotted end washer 52 is then slipped over the terminal blade 22, and brought up into contact with the yoke washer 44, the marginal slot 62 of the slotted end washer fitting over the lug 64 on the ferrule l8. The outer surface of the yoke washer 44 should then be flush with the surface defined by the outer end of the four nibs 50, if the bridge has been correctly adjusted. The cap i2 is then slipped over the terminal blade 22 and given about a quarter of a turn, which will serve to position the end washer 52 tightly against the yoke washer 44, and lock the parts together.

If the bridge adjustment, which controls the overall length of the terminal blade unit, is short, then the outer surface of the yoke washer 44 will lie within the surface defined by the outer ends of the four nibs 5B. This situation will be corrected automatically by the tightening up of the cap [2, for the reason that the wedge shaped embossings 58 will bear against the shoulders 14 and serve to lengthen the terminal blade unit.

This force, of course, is considerably greater than the friction by means of which the bridge 35 is gripped.

Subsequent variations in the length of either the tubing M or of the bridge 35, due to temperature or humidity conditions, will be taken up automatically by the frictional mounting of the bridge.

When the fuse blows, a gas pressure of as great as 200 pounds per square inch may be generated within a 200 ampere fuse, and this gas is vented outwardly through the clearances 69, 10 and H, at the right hand end of the fuse as shown in Fig. 3, and through the similar clearances, not numbered, provided at the left hand end of the fuse.

After the fuse has blown the parts may be disassembled, and a new fuse link substituted.

It will be noted that the casing I0 may be entirely removed, and the interior thereof presents a substantially flush surface which facilitates the cleaning of the interior of the fuse of any foreign matter which may have been deposited on the interior surface by the blowing of the fuse.

It will be noted that by welding the slotted end washer 5| of the yoke washer 43, and by upsetting the end of the terminal blade 2|, I have reduced the total number of separable parts from six to four, not including the fusible link. This is of advantage in that there are fewed separable parts to be mislaid, and it speeds up replacement of the fusible link in a measurable degree.

Although I have shown only one preferred embodiment of this invention, it will be understood that various modifications and changes may be made therein without departing from the spirit of my invention. The specification herein is descriptive only and it is understood that this invention is limited only by the appended claims.

I claim:

1. A cartridge fuse comprising a, casing, end caps therefor, a terminal blade assembly disposed within said casing and extending through said end caps, and means independent of said casing to secure said end caps to said terminal blade assembly against any longitudinal movement.

2. A cartridge fuse comprising a casing, end caps therefor, a terminal blade assembly disposed within said casing and extending through said end caps, and arcuate wedges on the end surfaces of said caps engaging with slots formed in said terminal blade assembly in interlocking relationship in order to hold said caps in spaced position with respect to each other.

3. A cartridge fuse comprising a casing, end caps therefor, a terminal blade assembl disposed within said casing and extending longitudinally through said end caps, said terminal blade assembly including rigidly mounted yoke Washers disposed within said casing at either end thereof, slotted end washers fitting over said terminal blade assembly and disposed adjacent to and exteriorly of said yoke washers, and means independent of said casing on said caps and on said terminal blade assembly to confine said end washers between said caps and said yoke washers in gas tight relationship to prevent the escape of gas in a longitudinal direction when the fuse is blown.

4. A cartridge fuse comprising a casing, end caps therefor, a terminal blade assembly disposed within said casing and extending through said end caps, means independent of said casing for securing said end caps to said terminal blade assembly against any longitudinal movement, and means to secure said caps to said casing.

5. A cartridge fuse comprising a casing, end caps therefor, a terminal blade assembly disposed within said casing and extending through said end caps, means for securing against any longitudinal movement said end caps to said terminal blade assembly independently of said casing, said terminal blade assembly including means for regulating the overall length thereof, and cooperative means on said casing and on said caps to prevent the spreading of said terminal blade assembly when the fuse is blown.

6. A fuse comprising a casing, a terminal blade assembly, two end caps for said casing, means to secure one end of said terminal blade assembly to one of said caps in gas-tight relationship, and means to secure th other end of said terminal blade assembly to the other of said end caps in gastight relationship, said casing being disposed between said two end caps and being held in place thereby to enclose the central portion of said terminal blade assembly.

7. A fuse comprising a casing, a terminal blade assembly having frictional means for adjusting the length thereof, two end caps for said casing, means to secure one end of said terminal blade assembly to one of said caps in gas-tight relationship, means to secure the other end of said terminal blade assembly to the other of said end caps said terminal blade assembly and means on said casing for engaging said two end caps to prevent outward movement of the same with respect to said casing.

8. A cartridge fuse comprising a casing, end caps engaging said casing in screw-threaded relationship, an adjustable bridge disposed within said casing and having a fusible link mounted thereon, terminal blades mounted on the ends of said adjustable bridge and in circuit with said fusible link and extending through said end caps, said terminal blades bein slotted for engagement with said caps to permit rotation of said caps through substantially 90 degrees, yoke washers secured to said terminal blades in gastight relationship, end washers disposed between said yoke washers and said end caps, said end caps having wedge shaped projections extending from the end surfaces thereof so as to lock said end caps and said end washers against said yoke washers in gastight relationship, and means to space said end washers from the edges of said casing to permit venting along the skirts of said end caps.

9. In a cartridge fuse having a casing and a terminal blade assembly, stamped sheet metal ferrules secured to said casing, stamped sheet metal caps fitting over said ferrules and through which said caps said terminal blade assembly extends, means for interlocking said caps and said ferrules, and additional means for interlocking said caps and said terminal blade assembly in gas-tight relationship.

10. In a cartridge fuse having a casing and terminal blade assembly, stamped sheet metal ferrules secured to said casing, stamped sheet metal caps fitting over said ferrules and through which said caps said terminal blade assembly extends, said caps and said ferrules being provided with, on their cylindrical surfaces, cooperating stamped portions for interlocking the same, and additional means for interlocking said caps and said terminal blade assembly in gas-tight relationship, both of said interlocking means being of a type which is operative by less than half a turn of said cap after it has been slipped over said terminal blade assembly.

11. In a cartridge fuse having a casing and a terminal blade assembly disposed therein and having extended blade portions provided with transverse slots, stamped sheet metal ferrules secured to said casing, stamped sheet metal caps fitting over said ferrules and through which said caps said blade portions extend, cooperating projections stamped in the opposed cylindrical surfaces of said caps and said ferrules for interlock-- ing the same, and arcuate shaped projections stamped in the end surfaces of said caps for interlocking cooperation with the slotted portions of said blade portions.

12. In a cartridge fuse, a cylindrical casingv a terminal blade having a yoke washer secured thereto in gas-tight relationship, a slotted washer fitting over said terminal blade adjacent to said. yoke washer, a slotted cap for said casing fitting over said terminal blade adjacent to said slotted washer, said terminal blade having oppositely disposed slots formed therein and the slot in said cap being so shaped as to permit said cap to be rotated into an interlocking engagement with said terminal blade, said cap being provided with cinbossings for cooperation with the slots in said terminal blade for urging said cap and said slottcd washer into engagement with said yoke washer in gas-tight relationship, said slotted washer extending over an edge of said casing, anal the skirt of said cap being spaced from the wall of said casing, and means for spacing said slotted washer from the edge of said casing to permit venting therethrough and into the space between aid skirt and said casing.

13. A cartridge fuse comprising a casing, skirted end caps therefor, a terminal blade assembly disposed within said casing and extending through said end caps, means for securing sa d end caps to said terminal blade assembly in gastight relationship and means to secure said caps to said casing in spaced relationship so as to cause venting of the gases generated when the fuse is blown in a backward direction through the passageways formed between the skirts of said caps and said casing.

GUST A. BERTHEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,854,450 Cook Apr. 9, 1932 1,950,489 Glowacki Mar. 13, 1931 2,077,823 Carney Apr, 20, 193"? 2,168,791 Carney Apr. 8, 1939 2,113,169 Carney Apr, 5, 1938 1,845,756 LaMar Feb. 16, 1932 FOREIGN PATENTS Number Country Date 441,589 Great Britain Jan. 22, 1936 

